This application claims priority from U.S. Provisional Application 60/032,566, filed Oct. 31, 1996. The present invention relates to retreading tires, and, in particular, to an improved envelope and valve for retreading tires.
The art for retreading tires is well known. Generally, a tire carcass is provided; a vulcanizable, rubber-like material is placed on the outside of the tire carcass; and the new tread is placed on the outside of the rubber-like material. Then, wicking material is placed outside the tread; an envelope is placed surrounding the entire tire assembly; a vacuum is drawn on a valve on the envelope; and the assembly is placed inside a curing oven, where pressure and heat are applied. Then, the envelope is removed, and what remains is the retreaded tire.
There are several problems with this method. The use of wicking cloths requires the purchase of materials and requires labor to install the wicking cloths. Also, the wicking cloths often make an imprint on the tire during the curing process, resulting in the tire looking imperfect. Finally, staples and other retaining mechanisms used to hold the wicking cloths in place tend to pierce the envelope, reducing the life of the envelope and resulting in failed retreads if the hole in the envelope is not discovered before the retreading process occurs. This wastes a considerable amount of labor and materials.